Resin coated paper



March 14, 1961 A ANKE-NS ETAL 2,975,074

RESIN COATED PAPER Filed Feb. 14, 1957 ,0o/oer base jr/"9: 2

IN V EN TORS. #US/fn L. Janke/7J BY Freo, Hoerger Aother oily products.

candy and the like and for other packaging purposes in- United StatesPatent RESIN 'COATED PAPER Austin L. Jankens, Bay City, and Fred D.Hoerger, Midland, Mich., `assignors to The Dow Chemical Company,Midland, Mich., a corporation of Delaware Filed Feb. 14, 1957, Ser. No.640,290

16 Claims. (Cl. 117-76) ice cross-sectionally in Figure 2 of vtheaccompanying drawing. A coated paper container in accordance with theinvention is fragmentarliy illustrated in Figure 3 of the drawing.

Any paper or paper stocksuitable for wrapping purposes (as the type ofpaper stock or base that is conventionally utilized in the manufactureofY waxed paper products) or for the fabrication of liquid or othercontainers and packages may advantageously be resinror plastic coated inaccordance with the invention. yThe intermediate layer of thechlorinated polyethylene vresin may be applied and coated by anyconventional technique on the surface of the paper. Thus, calendering,knife spreading and the like techniques may be utilized with advantagefor this purpose. intermediate layer is relatively vnon-critical and maybe varied to best suit and meet the requirements of the paracteristics,exceptionally low water vapor and other gas and vapor transmittingproperties. Such a product, as

`i'sfapparent, has great utility (among other uses) as a wrappingmaterial, especially for and in connection with various foodstuffs aswell as being ideally suited for other packaging and protective wrappingpurposes. vention also relates to a method for providing such products.

In accordance with the present invention, superior The inresin coatedpaper products are comprised of a paper baseover which has been coatedan intermediate substrate layer of a chlorinated polyethylene resinthat, beneficially, has a combined chlorine content between about 25 and50 percent by weight, based on the weight of the halogenated polymer,and over which there is applied a superficial coating layer of ahaloethylene (prefby initially coating paper with a layer of ordinarypolyethylene and then, after the surface of Vthe Yfirst applied resinhas been specially treated by various techniques and chemicalmodifications to adapt it for receipt o-f a Saran resin coating,applying a superficial layer or top A coat of such resin over themodified polyethylene surface. However, in the manufacture of theproducts of the invention, no special surface treatment of theintermediate chlorinated polymer resin layer is required beforeapplication of the final coating of the haloethylene Y polymer resin.The coated paper products of the present invention are strong, tough andflexible and remain so even at relatively low temperatures. They arepossessed of a strong and effective bond between all ofthe individualcontiguous constituents ofthe composite structure.

In general, they have good clarity and acceptabletransparency,permitting printed paper stock to be satisfactorily employed in theirfabrication. They are especially effective as' wrappings for variousfoodstuffs, especially with meat, fowl, cheese and the like whosepossible dehydration, when they have been packaged,may present aproblem. The product may be employed Vwith excellent results as afreezer wrap. In addition, its Vnatural grease and oil resistance suitsit well forpackafging lard, fish and n lt may also be used for bread,l

" schematically depicted in perspective in Figure 1 and ticularcomposite article that is being fabricated. It has little, if any,bearing on the adhesion that is yobtained between the constituents ofthe coated product. V0f

course, enough resin must be employed in the intermedi-A ate layer tocompensate for any permeation ofthe 'paper base that may occur whileproviding an integral, enveloping intermediate substrate thereover. Formost purpogses, the intermediate chlorinated polyethylene resin Vlayerneed not have `a thickness that exceeds about 20- mils or so. And, whencoated wrapping paper and the ylike is being fabricated, it Y isgenerally beneficial for the average vthickness of theintermediatechlorinated polyethylene resin layer to be between about `0.5 and5 mils.

The chlorinated polyethylene resin composition for the in an unmodifiedform over the paper base, desired in particular instances. v- Thechlorinated polyethylene resin that is employedin the intermediate resinlayer in the practice of the present invention may be derived by thechlorination of 'polyethylene of any nature according to any suitablehalo- K 'v 'I genating technique including suspension, solution anddirect chlorinations ofthe parent Y ethylene polymer.

Thus, the parent polyethylenes from which the chlorinated resins arederived may, for example, be similari tof i those which are oftentimesknown as conventional high pressure polyethylenes and which aresometimesreferred to as being polythenes Such polymers may be obtained vi' by polymerizing ethylene in a basic aqueous` medium and4 in thepresence of polymerization-favoring quantitiesxof i oxygen under highpressures in excess of 500 or 1,000 atmospheres at temperatures whichmay be between'lSO and 275 C. Or, if desired, they may be similarto' themers ordinarily have greater apparent molecular weights (as may bedetermined from such of theirl characteristicsy as melt viscosities andthe like) in excess of about 40,000; densities of about 0.94-096 gramper cubic'cen-tirneter; 'i

andmeltin-g points at least in the neighborhod of C. They are ordinarilyfound lto have a mo're'crystalline nature than conventionalpolyethylenes andniay contain less than 3.0 and even less than 0.3methyl Yradi-^ cal-per 100 methylene groups` in the polymer molecule. VThe essentially linear and unbranched polymersof ethl ylene may b eobtained under relatively low pressures/"ofy l to 100 atmospheres usingsuch catalysts for polymerizing the ethylene as mixtures of strongreducingagents i and compounds of group IVB, V-B and VI-'B metals of ythe periodic system; chromium oxide on silicated alumina; f hexavalentmolybdenum compounds', and charcoal 'supff ported nickel-cobalt. Thehaloethylene polymer 2,975,074 Patented Mar. 14, 1961` The thickness ofthe Y resinV employedV 'i ance with the invention.

ing the surface of the intermediate substrate layer of chlorinatedpolyethylene resin on the paper base may ad- Avantageously bepolyvinylchloride or aV copolymer of vinylchloride and vinyl acetatecontaining at least about 80 percent by Weight o-f vinyl chloridepolymerized in the copolymer molecule. Or it may be a Saran copolymer of-vinylidene chloride and vinyl chloride, a saran copolymer of vinylidenechloride and acrylonitrile or a saran -copolymer of vinylidene chlorideand acrylic acid or its ester derivatives including methyl acrylate,ethyl acrylate andthe like. It is particularly advantageous to employcrystalline saran copolymers and even more advantageous, in manyinstances, to utilize such copolymers of vinyl -chloride and vinylidenechloride as may contain at least -about 80 percent by weight ofvinylidenecnloride polymerized in the copolymer molecule or suchcopolymers lof vinylidene chloride and acrylonitrile (vinyl cyanide) beemployed suitably as the haloethylene polymer resins in the practice ofthe invention. as it is intended to be constructed in the heretoappended As herein employed, and

claims, the term haloethy-lene is intended to be eXclu sive ofiodine-containing compounds.

The haloethylene polymer resins may be utilized suitably in several waysin order to obtain a superficial layer of the top coating resin onintermediate substrate layer of the chlorinated polyethylene resin thatcovers the paper base. They may be cast on the surface of thechlorinated polyethylene resin from a dissolved composition that hasbeen formulated with suitable solvents, such as in lacquer formulations,or they may be deposited from latex compositions or with polymerizingmixtures of the monomerio substances which are polymerized in thehaloethylene polymer resin. ln order to secure better adhesion whenlatex compositions are employed, it may be beneficial to utilize a flametreatment or the like on the uncoated chlorinated polyethylene resinsurface to augment its wettability. The casting may be accomplished byvarious spread, dip, brush or spray techniques. lAfter theirapplication, the haloethylene polymer resin compositions may be dried,cured or treated according to usual and conventional techniques toremove orV countereffect solvents, vehicles or other admixed ingredientsand to effect a solid deposition of the tightly adhering resin layer inthe composite structure.

Advantageously, the casting of the haloethylene polymer resins to finishthe coated paper products may be performed suitably by spread coating adissolved or lacquer formulation of the haloethylene polymer resin overthe intermediate layer of the chlorinated polyethylene resin. Whiledifferent thicknesses may also be beneficial, it is desirable for thesuperticially applied layer of halo ethylene polymer resin on thesurface of the intermediate substrate layerof the chlorinatedpolyethylene resin to be at least about 0.02 mil thick and even moredesirable for many applications for it to have a thickness between 0.1and 2.0 mils. As is apparent, Wrapping papers may, if desired, be coatedon both of their surfaces in accord- In a similar manner, all of thecoatable surfaces of other articles such as both o-f the inner and outersurfaces of containers and the like or either surface or any desiredportion of a particular paper base may, as desired, be provided with theintermediate chlorinated polyethylene resin and superficial haloethylenepolymer resin coatings.

By way of illustration, separate specimens of wrapping paper were coatedwith intermediate layers of two different chlorinated polyethylenecompositions using halogenated resins having different total combinedchlorine con- -t tents. The chlorinated polyethylenehas been obtained byhalogenating an aqueous suspension of finely divided linearpolyethylene. The chlorinated resins were each blended with about 2percent by weight of a conventional plasticizer and 0.6 percent byweight of a conventional heat stabilizer. The chlorinated polyethylenecompositions were then knife coated on the paper to form 2 milintermediate layers which therethen surface coated with about a 0,l millthick top coat of a copolymer of vinylidene chloride vand acrylonitrilethat contained about 89 percent by weight of vinylidene chloridepolymerized in the copolymer molecule. The haloethylene polymer resinwas applied to the surface of the coated paper from a lacquercomposition with methyl ethyl ketone. After the coatings had dried oneach of the samples that were prepared, the resulting structures weretested for the adhesive properties of the applied coatings on the paperbase at room temperature by an adhesion test which comprised pressingabout a one-half by six inch strip of conventional regenerated celluloseadhesive tape of the pressure-sensitive variety (such as that whichisobtainable under the trade-name Scotch Brand from the Minnesota Miningand Manufacturing Comp-any) on the coated surface and measuring, asclosely as possible, the force in grams on the tape that was required topeel the superiicially applied saran coating from the surface of theintermediate layer of chlorinated polyethylene resin. Due tothe variousfactors involved, the accuracy of results in such a test is believed tofall within plus or minus 2O percent of the actual numerical valuesobtained. However, the test is valuable and reliable to a great extent`to indicate the `bonding efficiency between an applied coating and itssubstrate. ln the following Table l there is given the relative4adhesion values that were obtained in the testing for each of thecoated paper samples which are also distinguished one `from another bythe combined halogen contents that were present in the chlorinatedpolyethylene intermediate layer substrates. rl`he latter, incidentally,were strongly and firmly bonded to the paper base.

Table Adlzesio/'z of Scl-ron coating 0n paper base coated withintermediate layer of various chlorinated polyethylene resins Percent bywt. of Relative adhesion Sample Combined Chlorinc In Grams of Saran InResin In Inter- Coating mediate Layer "AL, 1a 10 B 37 50() Table11.--Adhes0n of saran coating lo intermediate substrate layers ofvariouschlorinated polyethylene resins Percent by Wt. of Relative AdhesionSample Combined Chlorine In Grams Ot' Saran In Resin Substrate Coating27 100 30 ll) 37 700 40 B00 45 l2() 50 40 l This resin was not the sameas that employed in the intermediate layer of Sample 1B although it hadabout the same combined chlorine Besides the foregoing, the gastransmission of a 1 mil base chlorinated polyethylene film coated with0.1 mil of the above saran resin was tested with oxygen and carbondioxide so as to give an indication of the excellent barrier propertiesobtainable in the coated paper products of the invention. Thetransmission rates of the lilm sample with the gases were found to beonly about 50 cubic centimeters ofoxygen and 160 cubic centimeters ofcarbon dioxide at room temperature per 100 square inches of the lm overa 24 hour period with one atmosphere of gas pressure differential acrossthe film. In comparison, the rates for a plain 1 mil lm of polyethylenewere found to be about 240 cubic centimeters of oxygen and 1940 cubiccentimeters of carbon dioxide by the same test.

All of the plastic coated paper products in accordance with theinvention had good flexibility and were resistant to embrittlement attemperatures asy low as -20 C. Besides this, their effectiveness aswater vapor barriers was commensurate to that which is obtainable fromconventional saran films.

The foregoing excellent results may be duplicated when other paper basearticles besides wrapping sheets, such as containers and the like, aresuperiicially coated with other haloethylene polymer resin compositionsusing other types and varieties of chlorinated polyethylene resins forthe intermediate substrate layers in the composite articles. Hence, thescope and purview of the invention is to be interpreted and construed inthe light of the hereto appended claims rather than being strictlygauged from the foregoing illustrative description and specification.

What is claimed is:

1. As a composite structure, a resin coated paper product whichcomprises a paper base having a continuous intermediate substrate layerof a chlorinated polyethylene resin applied thereover, said chlorinatedpolyethylene resin in said intermediate layer having a combined chlorinecontent between about 25 and 50 percent by weight, based on the weightof the chlorinated resin, and a continuous tightly adhering superficialcoating of a haloethylene polymer resin over the surface of saidintermediate layer, said haloethylene polymerbeing comprised of ahalogen of atomic number from 9 to 39 and selected from the groupconsisting of vinyl halide polymers that contain in the polymer moleculeat least about 80 weight percent of a polymerized vinyl halide andvinylidene halide polymers that contain in the polymer moleculev atleast about 60 weight percent of polymerized vinylidene halide.

2. The composite structure of claim 1, wherein the combined halogencontent of the halogenated polyethylene resin in the intermediate layeris between about 30 and 45 percent by weight.

3. The composite structure of claim 1, wherein the combined halogencontent of the halogenated polyethylene resin in the intermediate layeris between about 35 and 40 percent by weight.

4. The composite structure of claim 1, wherein the tightly adheringsuperficial coating haloethylene polymer resin has a thickness betweenabout 0.1 and 2 mils.

5. A wrapping paper product in accordance with the composite structureset forth in claim 4, wherein the thickness of the halogenatedpolyethylene resin in the 6 intermediate substrate layer s not in excessof about 20 mils.

6. The composite structure of claim 1, wherein the haloethylene polymerresin is a copolymer of vinyl chlo-l ride and vinyl acetate.

7. The composite structure of claim 1, wherein the haloethylene polymerresin is a copolymer of vinylidene chloride and vinyl chloride.

8. The composite structure of claim 1, wherein the haloethylene polymerresin is a copolymer of vinylidene chloride and acrylonitrile.

9. The composite structure of claim 1, wherein the haloethylene polymerresin is a copolymer of vinylidene chloride and methyl acrylate.

10. The composite structure of claim 1, wherein the haloethylene polymerresin is a crystalline vinylidene chloride polymeric material.

11. Method for coating paper which comprises covering the surface of apaper base with a continuous intermediate substrate layer of achlorinated polyethylene resin that has a combined halogen content,based on the weight of the chlorinated resin, between about 25 andpercent by weight, and subsequently coating the surface of the appliedintermediate layer with a continuous superficial layer of a haloethylenepolymer resin, said haloethylene polymer being comprised of a halogen ofatomic number from 9 to 39 and selected from the group consisting ofvinyl halide polymers that contain in the polymer molecule at leastabout 80 weight percent of a polymerized vinyl halide and vinylidenehalide polymers that contain in the polymer molecule at least about 60weight percent of polymerized vinylidene halide.

12. The method of claim 11, wherein the paper base is covered with anintermediate substrate layer of halogenated polyethylene having acombined halogen content between about 30 and 45 percent by weight.

13. The method of claim 12, wherein the paper base is covered with anintermediate substrate layer of halogenated polyethylene having acombined halogen content between about 35 and 40 percent by weight.

14. The method of claim l2, wherein the intermediate substrate layer ofhalogenated polyethylene resin has an average thickness that is not inexcess of about 20 mils.

15. The method of claim 12, wherein the superficial v layer of thehaloethylene polymer resin has a thickness of at least about 0.02 mil.

16. The method of claim 12, wherein the superficial layer of thehaloethylene polymer resin has an average thickness of between about 0.1and 2 mils.

References Cited in the tile of this patent UNITED STATES PATENTS

1. AS A COMPOSITE STRUCTURE, A RESIN COATED PAPER PRODUCT WHICHCOMPRISES A PAPER BASE HAVING A CONTINUOUS INTERMEDIATE SUBSTRATE LAYEROF A CHLORINATED POLYETHYLENE RESIN APPLIED THEREOVER, SAID CHLORINATEDPOLYETHYLENE RESIN IN SAID INTERMEDIATE LAYER HAVING A COMBINED CHLORINECONTENT BETWEEN ABOUT 25 AND 50 PERCENT BY WEIGHT, BASED ON THE WEIGHTOF THE CHLORINATED RESIN, AND A CONTINUOUS TIGHTLY ADHERING SUPERFICIALCOATING OF A HALOETHYLENE POLYMER RESIN OVER THE SURFACE OF SAIDINTERMEDIATE LAYER, SAID HALOETHYLENE POLYMER BEING COMPRISED OF AHALOGEN OF ATOMIC NUMBER FROM 9 TO 39 AND SELECTED FROM THE GROUPCONSISTING OF VINYL HALIDE POLYMERS THAT CONTAIN IN THE POLYMERIZEDMOLECULE AT LEAST ABOUT 80 WEIGHT PERCENT OF A POLYMERIZED VINYL HALIDEAND VINYLIDENE HALIDE POLYMERS THAT CONTAIN IN THE POLYMER MOLECULE ATLEAST ABOUT 60 WEIGHT PERCENT OF POLYMERIZED VINYLIDENE HALIDE.